1988 burb trans problem...any thoughts.?

[arizona kid]

I have a problem with a 1988 4x4 Surburban I just bought and wondered if anyone had any suggestion or comments to help me out. I am a new buyer to Chevy and the Surburban model. While I was driving I had a hard shift from 1st to 2nd in my automatic transmission. It was more like a jump. Then it seemed to be stuck in one gear (1st) and was winding out at high rpms yet not switching gears. I put into 4 wheel drive and experienced the same problem with the truck not getting out of 1st gear. Is this a major transmission problem ? I am inclined to fix it yet am new to fixing tranny problems. Any suggestions to what may have happened.....or anyone with knowledge of this type of problem please reply. Thx azkid

[68 Suburban]

I had the same think happen about 10 years ago to a 85 blazer I had. The trans pump ended being shot.

[Russell]

Hmm...

The suburban you have likely has the 700r4 overdrive transmission right (its the only overdrive tranny that was ever installed from the factory in the older subs minus a rare standard overdrive transmission)

The 700r4 is known to be notoriously weak, and breaks often. But before you give up all hope, make sure that all your vaccum lines are hooked up, and make sure that your motor is making enough vaccum to actually be able to run the transmission. They shift depending on the amount of vaccum they've got. So check to see if that steel line has been broken off, torqued, or if the rubber seals on the line are rotted out and not holding any vac anymore. Another possibility is that the little shifting linkage on the steering column can occassionally get messed up and not accurately show what gear you are in. When you shift into drive, count the number of clunks you hear to make sure that you are infact in drive, and not in first or something.

If all this fails, you may be out to find yourself a new transmission. Definitly a fun swap to say the least, but far from impossible if you have some simple tools, and some time to work on the burb. If you don't have a 700r4 tranny, this may be a good time to find one, get it built up a little bit (they can be built to withstand up to 700 hp now using corvette servos etc) and get it installed. The overdrive would help you wouth with your gas milage immensely! If you are planning on doing a lot of offroading, and generally like beating on your transmission, you'll want to get GM's heavy duty transmission, the TH400, its nearly bulletproof, and it will take a real beating before it breaks. All these transmissions can be found in your local wrecking yard, and often they will help you pull it out of the donor vehicle, if not do it for you at a certain fee.

Now, since you have a 4x4, you'll have to make sure that you get a 4x4 transmission -- the ones from a 2wd won't fit properly, you'll also want to make sure that if you get a 700r4 (and don't already have one), that you get one of the ones that doesn't require a computer to operate, just vaccum, and a manual lockup that you can install on a switch inside of your burb. I think that it is the pre 85 700r4s that you want (don't hold me to that though, I'm not 100% sure about it...) If you already have a 700r4, make sure that you get one with all the same connections as your current one already has.

Changing it out is a matter of either pulling the whole engine out, or removing your driveshafts, unbolting the tranny, and pushing it backwards a bit with a jack under both it and your motor, then lowering the jack, and putting the new one into place. There are several members here who have done this swap recently, and I'm sure that many would be plenty willing to give you some pointers if you need them.

I personally would just pull the whole engine, but being an 88, you most likely have a LOT of pollution controls that my 80 pickup doesn't have.

I hope this helps you out a little bit, and I hope that I am right in everything that I said. If not, I'm sure that there will be someone who corrects me and sets things striaght.

BTW -- Welcome to the Chevy / GMC truck forum, there are some really really wicked rides here, some that have been featured in magazines, down to some kids like myself who are trying to make something nice out of their old beaters

[arizona kid]

I really appreciate the help and time ya put into your reply. I look forward to talking to you on my progress with my transmission problem. Feel free to message me whenever Russell and thx again. My next step is to look at the vaccum line like you said. Plus my steering column does have a slight crack across it....maybe this is the major problem ?? I can only hope so.

[swervin ervin]

700R4's don't use vacuum to shift. They use throttle valve cables. Check the TV cable to make sure it's adjusted correctly.

http://www.73-87.com/7387garage/drivetrain/tvcable.htm

[Russell]

Ah, thanks Mike!

I've never had a 700r4 myself, so I kinda figured that they all ran fairly similar, hehe

[KShortell]

The TH700R4 is actually a pretty good transmission. I personally think that a lot of the criticism of it is a bit unfair-- people putting it behind "built" motors making more torque than the tranny was set to handle in stock form, etc. I've been towing with mine for years without problem. Of course, I've also changed fluid and filter roughly every 2 years/25,000 miles, too.

The shifts are a bit crisper (particularly the 1-2 shift) these days, actually since I installed a tranny cooler. But, I haven't had problems and the thing keeps soldiering on with 130,000 miles/18 years now.

Like Mike suggested, check the Throttle Valve (TV) cable. Changing fluid and filter couldn't hurt, either. Other than that, it's really an internal thing, something that's above the head of the occasional weekend wrenchhead like me...

Good luck!

[ckhd]

I agree with the TV cable. If it's not right, strange things happen.

Also, 700r4s are particularly sensitive to correct fluid levels. I've been told that over-filling them is MUCH worse than them being a little low. Wouldn't hurt to change the fluid/filter too.

Make sure that your column is putting it solidly in gear. When you have the pan off to change the filter, put it in each of the 7 positions, and make sure that the pin is firmly in the detent (looks like a rooster comb). With a cracked column, you might not be gettting it in the right position.

That's all I can think of right now.

[ALASKA ALUMINUM BEAR]

first off russel-your a class act-thanks for the info---you hit it all on the head for most of the 700r4's...thanks a bunch for your time....while i have had 1 bad one i had 2 really great 700r4---one was the original from chevy on the 4x4 86 burb--i got-200k miles from that tranny---the second 700r4-i got from jet transmissions-for 1300 bucks and all i can say is--wow--what a tranny they put out......

so don't give up on your 700r4---just get the rite folks to rebuild it-or see if jet has a kit you can do your self with there enlarge add ons....or buy one from jet--the price is really right......good luck and again thanks russel---everyone on this board should present info like you,,,thanks again

aabear
john

[aquasharkey]

adjust that throttle valve cable properly! if you don't you'll be looking for a new 700R4.
the more you have the foot to the floor, the more line pressure the trans makes so the clutches don't slip. if you have it adjusted wrong or not hooked up at all, it'll be making too low a line pressure in the tranny, letting things slip, and cooking the trans

[dark-star]

yes check the tv cable also check the governer and make sure it is clean and moves freeely, one piece of garbage in there and it will lock you up as well. if you have garbage floating from the coller lines flush and fill, might find out if the tranny was rebuilt recently, i wrecked one by not cleaning the lines! jw

[brian770]

i love the 700r4, i have one ine my 89 sub with 227899 miles on it and have truely beat it for the last 50,000. no probs. its just now starting to get funky
brian770

[lovetorev]

I would suggest a Large trans cooler from B&M, Summit or good supplier. These Overdrives need to be kept cool to survive!